Determining the aerodynamic effects of ice accretion on aircraft surfaces is an important step in aircraft design and certification. The goal of this work was to develop a complete sub-scale wind tunnel simulation methodology based on knowledge of the detailed iced-airfoil flowfield
that allows the accurate measurement of aerodynamic penalties associated with the accretion of ice on an airfoil and to validate this methodology using full-scale iced-airfoil performance
data obtained at near-flight Reynolds numbers. In earlier work, several classifications of ice
shape were developed based on key aerodynamic features in the iced-airfoil flowfield: ice
roughness, streamwise ice, horn ice, and tall and short spanwise-ridge ice. Castings of each
of these classifications were acquired on a full-scale NACA 23012 airfoil model and the aero-
dynamic performance of each was measured at a Reynolds number of 12.0 x 10^6 and a Mach
number = 0.20. In the current study, sub-scale simple-geometry and 2-D smooth simulations
of each of these castings were constructed based on knowledge of iced-airfoil flowfields. The
effects of each simulation on the aerodynamic performance of an 18-inch chord NACA 23012 airfoil model was measured in the University of Illinois 3 x 4 ft. wind tunnel at a Reynolds
number of 1.8 x 10^6 and a Mach number of 0.18 and compared with that measured for the
corresponding full-scale casting at high Reynolds number. Geometrically-scaled simulations
of the horn-ice and tall spanwise-ridge ice castings modeled Cl,max to within 2% and Cd,min
to within 15%. Good qualitative agreement in the Cp distributions suggests that important
geometric features such as horn and ridge height, surface location, and angle with respect
to the airfoil chordline were appropriately modeled. Geometrically-scaled simulations of the ice roughness, streamwise ice, and short-ridge ice tended to have conservative Cl,max and
Cd. The aerodynamic performance of simulations of these types of accretion was found to be
sensitive to roughness height and concentration. Scaled roughness heights smaller than those found on the casting were necessary to improve simulation accuracy, resulting in Cl,max and
Cd,min within 3% and 5% of the casting, respectively.